Inactivation Kinetics of beta-N-Acetyl-D-glucosaminidase from Prawn (Penaeus vannamei) in Dioxane Solution

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Xiao-Lan Xie and Qing-Xi Chen^*

Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China; fax: 86-592-2185487; E-mail: chenqx@jingxian.xmu.edu.cn

^* To whom correspondence should be addressed.

Received April 7, 2004; Revision received May 11, 2004

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beta-N-Acetyl-D-glucosaminidase (NAGase, EC 3.2.1.52) catalyzes the cleavage of N-acetylglucosamine polymers. It is in the composition of the chitinases and cooperates with endo-chitinase and exo-chitinase to disintegrate chitin into N-acetylglucosamine. In this work, the effects of dioxane on the enzyme activity for the hydrolysis of p-nitrophenyl-N-acetyl-beta-D-glucosaminide from the prawn (Penaeus vannamei) have been studied. The results show that appropriate concentrations of dioxane can lead to reversible inactivation of the enzyme, and the IC₅₀ is estimated to be 1.1 M. The kinetics of inactivation of NAGase in the appropriate concentrations of dioxane solution has been studied using the kinetic method of the substrate reaction. The rate constants of inactivation have been determined. The results show that the free enzyme molecule is more fragile than the enzyme-substrate complex in the dioxane solution. It is suggested that the presence of the substrate offers marked protection of this enzyme against inactivation by dioxane.

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KEY WORDS: beta-N-acetyl-D-glucosaminidase, Penaeus vannamei, dioxane, inactivation kinetics

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